1. Field of the Invention
This invention relates to high load force transmission belts and, more particularly, to a transmission belt having a plurality of laterally self adjusting block bodies slidably mounted on an endless band, which belt is particularly adaptable to use in vehicles, such as automobiles, as well as in other environments in which speed change mechanisms are employed.
2. Background Art
High load transmission belts are generally categorized as either 1) pressure force transmission type or 2) tension force transmission type. The former employs a plurality of block bodies mounted in abutting relationship, each to two adjacent block bodies, slidably on an endless, multi-layer, flexible, steel band which is trained about a pair of cooperating pulleys. An exemplary belt of this type is shown in U.S. Pat. No. 3,720,113, to VanDoorne et al.
In the VanDoorne et al belt, the block bodies gather at the loosened side of the belt as block bodies enter into the grooves of the drive and driven pulleys. The block bodies entering the groove of the drive pulley press the gathered block bodies at the loosened side of the belt to thereby rotate the driven pulley.
In the above type of belt, the block bodies are not interconnected so that their relative positions are not fixed. That is, they are slidable independently of each other along the endless band. Consequently, it is necessary to align the block bodies with each other so that they move consistently and without interference into and out of the pulley grooves. Exemplary guiding structure to accomplish this end is shown in each of Japanese Patent Publication Nos. 57-58543 and 55-100443. The belts disclosed in each of these publications have cooperating projections and receptacles on adjacent block bodies. Each block body has oppositely facing leading and trailing faces. The projections are shown to be on the leading face of each block body.
In designing the belts with cooperating projections and receptacles, designers have dealt with two competing objectives. The first objective is to allow the projections to smoothly enter into and withdraw from the receptacles in operation. This is particularly a problem as the block bodies extend around the curvature of the pulleys. If the projections and receptacles were closely conforming, there would be detrimental interference between the block bodies as the projections moved into and out of the receptacles. To accommodate the belt curvature as the block bodies extend around the pulleys, the receptacles have been made sufficiently large to provide clearance for the projections. This has made difficult the achievement of the second objective of belt designers--that of preventing rattling between adjacent blocks. There is a substantial amount of play permitted between adjacent block bodies which, in use, may result in the block bodies rattling in the absence of perfect alignment therebetween.
Another problem that has plagued the industry is that of the projections fully withdrawing from the receptacles as the block bodies traverse the curvature of the pulleys. If the projections are too tightly received in the receptacles, the block bodies may not completely conform to pulleys, particularly small diameter pulleys. That is, the block bodies tend to bridge across the pulley grooves, which reduces the contact area between the block bodies and the cooperating pulleys. Too loose a fit between the projections and receptacles may result in the block bodies completely separating from each other resulting in misalignment of adjacent bodies and possible prevention of the projection from reentering the cooperating receptacle.
Another problem with the above-mentioned belt systems is that there is a substantial amount of friction generation between the endless band and the block bodies. In FIG. 1 of the drawings herein, a prior art system is shown schematically in which a lubricant is directed outwardly against a belt trained around a pair of pulleys to alleviate this problem. The lubricant is propelled at the point of entry of the block bodies into the driven pulley. The centrifugal force developed by the rotating pulleys causes the lubricant to spray radially outwardly so that much of the lubricant produces no beneficial effect.
In an exemplary belt system of the type described above, each block body has a base, a head, and a neck/pillar connecting between the base and head and defining a slot for reception of an endless band. The block bodies between the drive and driven pulleys are forcibly engaged at the heads and necks/pillars above an inclination line about which the block bodies pivot relative to each other in conforming to a pulley. In operation, there are vibrations which cause contacting block body portions to abrade each other. As a result, the block bodies may wear excessively over time, particularly in environments where the pressure between adjacent block bodies is substantial.
One solution to the above problem has been to increase the contact area between adjacent block bodies. This increases the pressure receiving surface area of each block body to reduce the force per unit area. While this solution does reduce the problem of wear, it also increases the belt weight and causes considerable increase in the centrifugal forces developed at high speed operation of the system. As a result, the transmission capability of the belt may be diminished.